TBT – Zeiss Lens History, Design & Modernity

Post by Paul Brodek our Used Equipment buyer

Zeiss is one of the trio of German powerhouse optical makers, along with Leica and Schneider Kreuznach. With some recent exceptions, Leica’s lenses are mostly destined for Leica cameras, made primarily in Leica lensmounts, while Zeiss and Schneider manufacture/d lenses in multiple mounts and formats. Both Zeiss and Schneider (and Leica, for that matter) make very high-end optics for the cine and video world, but Zeiss has much more presence than Schneider in the consumer market, so that’s who we’re looking at today.

As usual I have way too many words, so this has morphed into a two-parter. Zeiss intro and lens designs today, market scope and modern age offerings next time.

If you’re wondering why Zeiss is a throwback feature, start with the fact that Zeiss was founded in Jena in 1846. I’m far from a photo historian, but isn’t that kinda when photography was invented? Zeiss started with microscopes and microscope optics, so they had decades of optical and machining experience when cameras and camera lenses became a thing. There’s also the fact that the optical design of many lenses today are either identical to, or offshoots of, original Zeiss designs. Zeiss lenses were paired with camera bodies from other manufacturers, names you may have heard of like Exacta, Hasselblad and Rollei, and untold  number of obscurities. Formats covered ranged from subminiature to large format, and Zeiss medium- and large-format lenses found their way onto countless folding cameras. Zeiss began manufacture of their own cameras in 1902, under the Zeiss Ikon name, with Ikonta/Super Ikonta folders and Contax/Contarex/Contaflex 35mm cameras the best known.  
And so’s now the time to seque into nerd-dom. Just like all of be-bop was laying down different melodies on top of the chord changes from Gershwin’s _I Got Rhythm_, (hot dang!), many modern lens designs are based on three Zeiss designs for wide lenses, and 3 designs for normal/tele lenses. There’s some terminology involved, which I’ll try to keep meaningful but simple. 

First off, lenses are composed of multiple lens elements, meaning polished pieces of glass, assembled into groups. An element might stand alone as its own group, or could be glued to other elements. The most basic reference to lens design starts with the number of lens elements, followed by the number of optical groups. Kinda like how the wheel/truck layout of a steam locomotive engine clues you into its size and purpose (a simple 0-2-2 vs a massive 2-14-2, anybody???). 4 elements in 4 groups (4e/4g) is a much simpler design than 15 elements in 12 groups (15e/12g). There’s a lot more optical science than I understand to how and where elements and groups are located, but I think it’s safe/instructive here to look at it simply in terms of increasing complexity.

Elements/groups can be oriented symmetrically front/back of the aperture mechanism, meaning a cross-section of the elements/groups looks the same on both sides of the aperture, or non-symmetrically. A symmetric design usually allows a faster maximum aperture, but can introduce distortion and aberrations (optical flaws) that are more easily controlled with non-symmetric designs. 

We have different lens designs to give different fields of view (wide, normal, tele), to correct for different aberrations and distortions, at varying maximum apertures. A perfect lens, which doesn’t exist, would have zero aberrations, zero distortion, and a maximum aperture of f/0.??? I don’t even know! There already exist f/1.2, 1.1, 1.0, 0.95. Well, really really really fast. 

Lens designers balance all this stuff to give the best possible performance, with known compromises and imperfections.

The Big 6 Zeiss lens designs follow. I’ll hit the designs by type and date, to show how far back they reach.

Normal/Tele:Planar (1896) 6e/4g: The first modern normal/tele lens design, with a symmetric optical layout allowing for relatively fast apertures, important 100+ years ago when even fast film was S-L-O-W. Back in 1896 a maximum aperture of f/5.6 or 4.5 was fast, and Planars got you there. As glass formulas and lens coating improved, we commonly see Planars are f/2, with later ones reaching f/1.5 and f/1.4. The Planar has a fairly flat field, with low linear distortion and fairly even sharpness from the center of the frame to the corners.

But the Planar design has a lot of glass, and a lot of glass-to-air surfaces. That makes it a relatively heavy, expensive design, that requires very good lens surface coatings to minimize flare and enhance contrast. It took 30-50 years before coating technology would advance enough to maximize the benefits of the Planar design, and get us to those f/2 and faster maximum apertures. Correcting the increasing number of aberrations at those faster apertures also required more elements, so 7-8e Planar designs became common.

Tessar (1902) 4e/3g: A simpler normal/tele design with a non-symmetric layout, the Tessar was smaller, lighter and cheaper to manufacture than the Planar. Fewer glass-air surfaces meant lens coatings weren’t as critical. As to compromises, look to losing some of the benefits of the Planar: a curved field means more sharpness fallout to the corners. Tessars usually need to be stopped down 2-3 stops for the corners to get sharp. The non-symmetric design means you won’t find Tessars any faster the f/2.8, with many opening to only f/3.5.

Sonnar (1932) 7e/3g: This is a Tessar derivation, with some extra glass to improve on the Tessar shortcomings. The Sonnar allows for faster apertures than the Tessar, while better contrast and less flare than the Planar, due to smaller number of glass-air surfaces. But the Sonnar has a much deeper rear element than either Planar or Tessar, so it gets in the way of SLR mirrors, limiting use to rangefinder cameras, and, in our whizz-bang modern digital age, mirrorless digital cameras.

Wide-Angle Lenses:Biogon (1936) 8e/5g: The first modern wide lens design. Compared to the normal/tele lenses, you can see that wides need more glass, and more complex designs. The Biogon is a very compact design, with a deeply-recessed rear element. Like the Sonnar, that makes it a rangefinder-only lens in the film world, mirrorless-only for digital. It has excellent contrast and corner-to-corner sharpness, but there’s a fair amount of darkening, or vignetting, as light falls off to the corners. Biogon designs also tend to do poorly adapted to digital bodies, with the corner light fall-off causing visibly softer corners and weird color shifts in the corners.

Distagon (1953) 10e/10g: Designed in part for SLR use, the Distagon rear element clears an SLR mirror. Though a non-symmetric design, the larger overall size often gives faster maximum apertures than Biogon. This also gives us a curved field and more aberrations to correct for, so the Distagon designs grew more complex: 13-15 elements in 12 groups is common. That means many more glass-air surfaces, requiring better lens coatings to maintain contrast and prevent flare.

Hologon (1966) 3e/3g: An ultrawide lens design, with big honking complex lens elements, a very deep rear element and a fixed, slow aperture. Very flat field, very low distortion and aberrations. But heavy vignetting, with corners 2-3 stops darker than the center. Zeiss usually supplied Hologons with special center filters, 2-3 stops darker in the center, to even out the light fall-off. Which meant your nominally f/8 lens was actually shooting at f/11 or f/16. There’s not a lot of Hologons out there, none longer than 15mm.

So that’s a lotta stuff. Zeiss is very proud of their optical designs, both in terms of what they are, and how far back in history they go. New Zeiss lenses today still carry those same design designations, and the lens boxes invariably have a lens design cross-section to show how cool the innards look. Check out the lenses, and boxes, in the pix.

Next time: film/digital, Germany/Japan, Zeiss manages to stay alive and relevant in the 21st century.

Leave a Reply

Your email address will not be published. Required fields are marked *